Stabilization of hydrocarbon distillates



nited States Patent Ufifice STABILIZATION F HYDROCARBON DISTILLATES Joseph A. Chenicelr, Bensenville, 111., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application July 25, 1951, Serial No. 238,567

2 Claims. (CI. 44-74) The invention is particularly applicable to the stabilization of burner oils which undergo discoloration and form undesirable sediment in storage. Burner oils are marketed under various trade names such as fuel oil, furnace oil, burner oil, diesel fuel, jet fuel, etc. and are selected to meet commercial specifications. It is understood that the term burner oil is used in the present specification and claims in a generic sense to include hydrocarbon distillates heavier than gasoline. In general, these hydrocarbon distillates will have initial boiling points ranging as low as 300 F. and end boiling points which may range up to 750 F. or more.

Discoloration of burner oil is undesirable because marketing of the burner oil in most cases includes a color specification. It is, therefore, important that the burner oil does not undergo discoloration in storage. Similarly, the formation of sediment in burner oil is objectionable because the sediment tends to plug strainers, burner tips, injectors, etc., and when used as diesel fuel, tends to form varnish and sludge in the cylinders of the diesel engine. The sediment referred to herein is different from the solid material originally contained as such in burner oil and referred to in the art as B. S. & W. The sediment with which the present invention is concerned is not contained in the burner oil as produced but forms during storage.

At the present time burner oils come primarily from non-destructive distillation of petroleum oil, commercially referred to in the art as straight run distillates, and from catalytic and non-catalytic cracking processes, commonly referred to in the art as cycle stocks. The term cycle stocks is used because the burner oil is separated from a fraction which is recycled to the cracking process for further conversion therein. Other sources of burner oil may include those produced by the reaction of carbon monoxide with hydrogen, etc. Regardless of the source, many of the burner oils are unstable in storage and undergo discoloration and sediment formation. This is particularly true in blends of straight run petroleum distillates and cracked hydrocarbon oils, particularly catalytically cracked hydrocarbon oils, all being heavier than gasoline. Because of the increased amount of cycle stocks available, many refiners are marketing blended burner oils and, therefore, require some method of preventing the undesirable deterioration.

In a specific embodiment the present invention relates to a process for retarding sediment formation and discoloration of burner oil in storage, which comprises adding thereto from about 0.0001% to about 1% by weight of S-benzyl isothiourea.

In still another specific embodiment the present invention relates to a process for retarding discoloration of a blend of straight run petroleum distillate and cracked hydrocarbon oil, both heavier than gasoline, which comprises adding thereto from about 0.001% to about 0.1% by weight of an additive as herein set forth.

In another embodiment the present invention relates to burner oil, containing, as a-retardant of saiddeteriora- 2,717,826 Patented Sept. 13, 1955 tion, a minor amount of an additive as herein set forth.

In the interest of simplicity, the following specifications will be directed primarily to the treatment of burner oil.

The isothiourea compounds for use in accordance with where X is sulfur, and where R, R1, R2 and R3 are selected from the group consisting of hydrogen, hydrocarbon groups and substituted hydrocarbon groups.

Where X in the above general structure is sulfur, the additive of the present invention will comprise an isothiourea compound. Specific compound includes S-benzyl isothiourea.

The additive of the present invention may be prepared in any suitable manner. For example, S-benzyl isothiourea may be prepared by the reaction of thiourea and benzyl chloride in alcoholic solution to yield S-benzylisothiouronium chloride which is then treated with an equivalent of potassium hydroxide solution to yield the desired S-benzyl isothiourea.

As hereinbefore set forth, the novel process of the present invention is particularly applicable for the stabilization of burner oils. However, it is understood that this process also may be used for the stabilization of gasoline and more particularly unsaturated gasolines, including cracked gasoline, polymer gasoline, etc., as well as to the treatment of aviation gasoline which tends to undergo deterioration due to the addition of tetraethyl lead fluid or other components in the gasoline.

The additive, of the present, invention is generally added to the organic material in an amount of less than about 1% by weight and more generally within the range of from about 0.0001% to about 1% and preferably of from about 0.001% to about 0.1% by weight. It. is understood that these additives may be used alone or in conjunction with other additives employed for specific purposes depending upon, the particular organic material being treated. For example, in the treatment of burner oil, these additives may be used in conjunction with antioxidants which may comprise aliphatic amines, amino alcohols, etc., metal deactivators, corrosion inhibitors, dyes, etc. When used in gasoline, the additive may be employed along with antioxidants, particularly of the phenolic, amino phenolic, or phenylene diamine type, metal deactivators, dyes, anti-knock agents including tetraethyl lead, etc.

When the additive of the present invention is a liquid at atmospheric conditions, it readily may be incorporated in the organic material. When desired and particularly when the additive is not liquid, it may be utilized in a suitable solvent, including hydrocarbons, alcohols, glycols, ethers, etc. and, in such cases, the additive may be prepared as a solution in the solvent and marketed in this manner along with any other component or components to be included in the mixture as hereinbefore set forth.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

EXAMPLE I This example illustrates the beneficial effects of the preferred S-benzyl isothiourea in retarding discoloration of burner oil. The additive was prepared by the reaction of benzyl chloride with thiourea followed by neutralization with caustic in the manner hereinbefore set forth.

Discoloration of the burner oil was determined in an accelerated test, which avoids the necessity of running long time storage tests in order to determine the effect of the various additives. In other runs it has been found that this accelerated test correlates quite satisfactorily with the long time storage'test and, therefore, gives a true picture of the stability of the fuel. The samples of the fuel oil were stored at 100 C. for 20 hours. The color was determined in a Lumitron, Model 402-E, Spectrophotometer, and the data are reported as the per cent transmittance. It is apparent that the per cent transmittance is inversely proportional to discoloration, and that high per cent transmittance means low discoloration.

S-benzyl isothiourea was added in an amount of 0.002% by weight of a sample of the burner oil. This sample and a sample not containing this additive, were tested in the accelerated test described above. The results are shown in the following table:

Table 1 Percent Additive Transmittanee None S-benzyl isothiourea EXAMPLE II This example illustrates the beneficial eifects obtained by the use of the additive of the present invention in reducing sediment formation in burner oil. Burner oil used in this example was the same as that described in Example I. The sediment was determined by an accelerated test in which a sample of the burner oil is exposed to light from a carbon arc lamp for 90 minutes under controlled conditions. The sample is then filtered and the sediment content determined by weighing.

0.01% by weight of the additive was added to another sample of the fuel oil and, after testing in the manner described herein, the sample containing the additive and a sample without the additive had the following sediment contents:

Table 2 Sediment, Additive mg. per

None 3. 2 S-benzyl isothiourea 0. 5

The additive to be used in this example comprises S- ethylhexyl isothiourea and may be utilized in a concentration of 0.005% by weight to retard deterioration of burner oil in storage.

S-dodecylphenyl isothiourea may be utilized in a concentration of 0.006% by weight to retard deterioration of burner oil in storage.

3-guanyl-2-octyl isothiourea may be utilized in a concentration of 0.005% by weight to retard deterioration of burner oil in storage.

3-guanyl-2-decy1 isourea may be utilized in a concentration of 0.007% by weight to retard deterioration of burner oil in storage.

3-guanyl-2-aminooctyl isourea may be utilized in a concentration of 0.005% by weight to retard deterioration of burner oil in storage.

EXAMPLE VIII As hereinbefore set forth, the accelerated aging test correlates very satisfactorily with long time storage tests. This example illustrates the results obtained in storage tests of different samples of a fuel oil, one containing the additive described in Example I and the other not containing this additive. The results to date of these storage tests are indicated in the following table:

Table 3 Sediment, mg. per m1. after 168 days in storage at 100 F.

Additive None Sbenzy1 isothiourea References Cited in the file of this patent UNITED STATES PATENTS 2,156,193 Puetzer Apr. 25, 1939 2,220,970 Loane et al Nov. 12, 1940 2,336,868 Jayne et a1 Dec. 14, 1943 2,618,605 Schaefier Nov. 18, 1952 2,624,762 Downey Jan. 6, 1953 2,626,207 Wies et a1. Jan. 20, 1953 

2. CRACKED GASOLINE CONTAINING, AS AN ADDITIVE TO RETARD DETERIORATION IN STORAGE, FROM ABOUT 0.0001% TO ABOUT 1% BY WEIGHT OF S-BENYL ISOTGIOUREA. 